This invention relates to a traffic signalling device, and in particular to a device for mounting on a school bus which provides improved safety to passengers crossing the street in front of the bus.
It is the law in many jurisdictions that oncoming traffic or traffic passing a school bus must stop in order to allow passengers who might wish to cross the street in front of a loading or unloading stopped bus, to cross with safety. In order to advise such traffic that the school bus is loading or unloading, the bus usually carries a stop sign, which may or may not include flashing lights. The stop sign is usually hinged to the side of a bus, and deployment is enabled by the bus driver. The stop sign is rotated about a vertical axis so as to lie flat against the bus when it is not to be displayed, e.g. when the bus is moving, and is rotated so that the plane of the sign faces oncoming or passing traffic when deployed. Safety signs of this type are described in U.S. Pat. No. 4,559,518 issued Dec. 17th, 1985, U.S. Pat. No. 4,339,744 issued July 13th, 1982, U.S. Pat. No. 3,094,683 issued June 18th, 1963, U.S. Pat. No. 3,133,265 issued May 12 th, 1964 and U.S. Pat. No. 4,138,668 issued Feb. 6th, 1979. The stop sign extends outwardly from the bus not much more than the width of the sign.
Buses loading or unloading passengers typically stop in the vehicle driving lane of a road. Consequently while automobiles in the overtaking lane usually see the stop sign and stop behind the school bus, automobiles in the oncoming lane usually do not see the sign and thus do not stop. This creates a very dangerous situation for school bus passengers crossing the road, who usually are small children expecting all traffic to stop.
U.S. Pat. No. 1,786,678 issued Dec. 3Oth, 1930 describes a long arm hinged to the side of the bus which can be extended outwardly into an overtaking lane of traffic. The arm is hinged so that it lies flat against the side of the bus when it is not deployed. While this traffic control arm extends much further into the line of sight of oncoming traffic, the deployment means is such that with substantial decelerating forces by the bus, the arm can automatically be deployed directly into the front of overtaking traffic, and therefore is subject to being smashed. In addition, it is located about halfway down the side of the bus and is subject to being smashed by any vehicle carrying a driver who does not notice it.
U.S. Pat. No. 4,543,905 issued Oct. 1st, 1985 describes a portable traffic signal having two telescopic arms, one of which raises a traffic signal to a position above the height of oncoming traffic, and the other of which carries the traffic signal outwardly directly above the oncoming lane of traffic. If this structure were mounted on a school bus, it would achieve the desired result of locating a traffic signal in the line of sight of oncoming as well as overtaking traffic, but it is not suitable for this function for several reasons. Firstly, the mechanism of the invention is complex and requires retraction along two separate axes. This takes an inordinately long amount of time, and the bus driver is usually in a great hurry. The retraction and deployment mechanism thus would be unsuccessful for use on a school bus since the bus driver would likely move his bus before the arms are fully retracted, causing acceleration forces to damage it.
If only the top telescopic beam of that design were used, mounted on the roof of a school bus, the traffic signal would be damaged when the school bus moves, due to acceleration, deceleration and wind forces on the traffic signal, as it is anchored at only one point, and the display has its plane constantly perpendicular to the axis of the traffic lane.
Due to the telescopic nature of the structure, a special pulley mechanism is required which takes up a large amount of space and is subject to binding or slackening due to differential heating or cooling in extremely cold or hot weather, wear of the cables, and jamming due to ice accumulation on the telescoping structural elements.
The result of the above is that the structure would be prone to damage when used on a school bus used in all types of weather, which repeatedly starts and stops, which rapidly loads and unloads passengers and which requires a robust traffic control sign which is repeatedly deployed and retracted.